KR20140050068A - Hydraulic pressure cylinder - Google Patents

Abstract

The fluid pressure cylinder of the present invention includes a cushioning mechanism for decelerating the piston rod near the stroke end of the piston rod with respect to the cylinder tube. The cushion mechanism is formed between a cushion bearing installed on the piston rod, a cushion cylindrical surface into which the cushion bearing enters the stroke end, a cushion gap formed between the cushion cylindrical surface and the cushion bearing to narrow the flow of working fluid, and a cushion gap. An orifice is formed having a bypass passage leading to a bypassing working fluid, and a resistor interposed in the bypass passage, the resistor narrowing the flow of the working fluid passing through the bypass passage.

Description

HYDRAULIC PRESSURE CYLINDER}

TECHNICAL FIELD This invention relates to the fluid pressure cylinder which slows down a piston rod in the vicinity of the stroke end of a piston rod in a cylinder tube.

A fluid pressure cylinder (hydraulic cylinder) used for a hydraulic excavator or the like has a cushioning mechanism for generating a cushion pressure near the stroke end of the piston rod to decelerate the piston rod.

JP8-61311A and JP11-230117A disclose a cushioning mechanism having a cushion bearing that defines a cushion gap through which a working fluid passes when a piston rod reaches near the stroke end. Inside the floating bearing cushion bearing, a cushion seal (seal) having a function as a check valve is interposed.

When the piston rod comes near the stroke end, the cushion bearing enters the inside of the cylinder head and a cushion gap is defined. Accordingly, since the working fluid flows out through the gap between the cushion gap and the cushion seal (orifice groove), the cushion pressure is generated by the resistance of the flow of the working fluid, and the piston rod is decelerated.

However, in the conventional cushion mechanism, since a dedicated cushion seal in accordance with the specification is interposed inside the cushion bearing, the cost of the product is increased, and the cushion is caused by dimensional deviation such as the gap (orifice groove) of the cushion seal. There is a possibility of deviation in performance.

Moreover, since the cushion seal groove which accommodates a cushion seal is formed in the outer periphery of a piston rod, groove processing is required for a piston rod.

An object of the present invention is to provide a fluid pressure cylinder capable of obtaining a predetermined cushion pressure without using a cushion seal.

According to one aspect of the present invention, there is provided a hydraulic pressure cylinder including a cushion mechanism for decelerating the piston rod in the vicinity of the stroke end of the piston rod with respect to the cylinder tube, the cushion mechanism being a cushion bearing provided in the piston rod, and the stroke end in the vicinity of the stroke end. A cushion gap formed between the cushion cylindrical surface into which the cushion bearing enters, the cushion cylinder surface and the cushion bearing to narrow the flow of the working fluid, a bypass passage leading to a working fluid bypassing the cushion gap, and a bypass passage. A fluid pressure cylinder is provided, having a resistor mounted therebetween, wherein the resistor is formed with an orifice that narrows the flow of working fluid through the bypass passage.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention and advantages of the present invention will be described in detail below with reference to the accompanying drawings.

1 is a sectional view of a hydraulic cylinder according to an embodiment of the present invention.
FIG. 2A is a sectional view of a hydraulic cylinder in which part of FIG. 1 is enlarged. FIG.
FIG. 2B is a cross-sectional view illustrating the cross section along AA of FIG. 2A.
3 is a cross-sectional view of a hydraulic cylinder showing a state in the stretching operation.
4 is a sectional view of a hydraulic cylinder showing a state in the contracting operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a cross-sectional view of a hydraulic cylinder 1 according to an embodiment of the present invention. The hydraulic cylinder 1 is used as an arm cylinder of a hydraulic excavator, for example, and the arm of a hydraulic excavator rotates when the hydraulic cylinder 1 expands and contracts.

The hydraulic cylinder (fluid pressure cylinder) 1 includes a cylindrical cylinder tube 10, a piston 20 partitioning the rod chamber 2 and the end chamber 3 into the cylinder tube 10, and a piston 20. Piston rod 30 is connected to).

The rod chamber 2 and the end chamber 3 communicate with a hydraulic source (working fluid pressure source) (not shown), and the piston rod 30 is driven by the working hydraulic pressure (working fluid pressure) derived from the hydraulic source. Move in the direction of (O) to stretch.

As the working fluid, for example, a water-soluble substitute may be used instead of oil.

At the open end of the cylinder tube 10, a cylindrical cylinder head 40 is inserted through which the piston rod 30 is slidably inserted. The cylinder head 40 is fastened by screwing an outer circumferential thread portion (male thread) 41 into an inner circumferential thread portion (female thread) 12 of the cylinder tube 10.

The cylinder head 40 has a cylindrical head fitting portion 42 fitted to the cylinder inner circumferential surface 11. The O-ring 9 and the backup ring 19 are interposed in the outer circumferential portion of the head fitting portion 42.

In the inner circumferential portion of the cylinder head 40, bearings 55, a sub seal 56, a main seal 57, and a dust seal 58 are interposed therebetween, and these are rod outer peripheral surfaces 31 of the piston rod 30. Makes a sliding contact. As the bearing 55 is in sliding contact with the rod outer circumferential surface 31, the piston rod 30 is supported to move in parallel in the direction of the central axis O of the cylinder tube 10.

A supply and discharge port 43 is formed in the cylinder head 40, and the supply and discharge passage 5 is partitioned by the supply and discharge port 43. The supply-discharge passage 5 communicates with a hydraulic source through the hydraulic piping not shown connected to the piping port 17 of the cylinder tube 10. FIG.

On the inner circumference of the cylinder head 40, a cylindrical head-shaped inner circumferential surface 44 is formed. One end of the supply / discharge port 43 is opened in the head inner circumferential surface 44, and a supply / discharge passage 5 is partitioned between the head inner circumferential surface 44 and the rod outer circumferential surface 31.

The holder 23 is interposed in the cylinder tube 10. The holder 23 is formed in an annular shape centering on the central axis O. As shown in FIG. The holder 23 is fitted to the cylinder inner circumferential surface 11 together with the head fitting portion 42 of the cylinder head 40. The O-ring 28 and the backup ring 18 are interposed in the outer circumferential portion of the holder 23.

The holder 23 has a cushioning cylindrical surface 24 as its inner circumferential surface. The cushion cylindrical surface 24 is formed in the cylindrical surface shape centering on the central axis O. As shown in FIG.

The holder 23 has its outer circumferential tapered portion fitted to the tapered surface 13 of the cylinder inner circumferential surface 11, and its upper end surface is in contact with and fixed to the head end surface 45 formed at the lower end of the cylinder head 40. do.

In addition, the fixing method of the holder 23 is not limited to this, For example, you may fix to the cylinder head 40 via the bolt not shown. In this case, it is not necessary to form the tapered surface 13 on the inner surface of the cylinder tube 10. In addition, the holder 23 may be integrally formed with the cylinder head 40.

In the contracting operation of the hydraulic cylinder 1 in which the piston rod 30 moves downward in FIG. 1, pressurized hydraulic oil supplied from the hydraulic source through the hydraulic pipe passes through the supply / discharge passage 5 to the rod chamber 2. Inflow.

On the other hand, in the expansion operation of the hydraulic cylinder 1 in which the piston rod 30 moves upward in FIG. It flows through the pipe and flows out to the hydraulic source.

The hydraulic cylinder 1 is provided with a cushioning mechanism 6 for decelerating the piston rod 30 when the piston rod 30 reaches the stroke end. 1 shows a state in which the piston rod 30 is in front of the stroke end and near the stroke end.

The cushion mechanism 6 is provided with the cylindrical cushion bearing 60 provided in the piston rod 30. When the piston rod 30 reaches near the stroke end, the cushion bearing 60 enters the inside of the holder 23, so that the cushion gap 4 (see Fig. 3) is partitioned therebetween. Resistance is imparted to the flow of the hydraulic oil which flows out from the rod chamber 2 through the supply / discharge passage 5 by the cushion gap 4 so that the pressure of the rod chamber 2 (hereinafter referred to as cushion pressure) rises. do. When the cushion pressure rises, the piston rod 30 is decelerated.

The cushion bearing 60 has a bearing outer peripheral surface 61 as its outer peripheral surface. The bearing outer peripheral surface 61 is formed in the cylindrical surface shape centering on the central axis O. As shown in FIG. The outer diameter of the bearing outer circumferential surface 61 is larger than the outer diameter of the rod outer circumferential surface 31 and smaller than the inner diameter of the cushion cylindrical surface 24. The cushion gap 4 is partitioned between the bearing outer peripheral surface 61 and the cushion cylindrical surface 24.

The cushion bearing 60 is formed with a cut circle 62 (cut out) in which the bearing outer peripheral surface 61 is partially cut. That is, the cut part 62 is a recess provided in the bearing outer peripheral surface 61. The width | variety of the cut | disconnected circular part 62 is formed so that it may become small toward the lower side of FIG. Accordingly, the passage cross-sectional area defined by the cut portion 62 of the cushion gap 4 gradually decreases as the piston rod 30 approaches the stroke end. The clearance (gap width) of the cushion gap 4 and the shape of the cut part 62 are set according to the deceleration characteristic calculated | required by the cushion mechanism 6.

The cushion mechanism 6 includes a bypass passage 50 for guiding hydraulic oil bypassing the cushion gap 4, and a resistor (set screw) 63 interposed in the bypass passage 50. An orifice 64 is formed at 63 to narrow the flow of hydraulic oil passing through the bypass passage 50.

The bypass passage 50 is partitioned by a bypass passage hole 25 that penetrates the holder 23. The bypass passage hole 25 extends substantially in parallel with the central axis O, and is opened in the upper and lower end faces of the holder 23, respectively.

FIG. 2A is an enlarged cross-sectional view of a portion of FIG. 1, and FIG. 2B is a cross-sectional view illustrating the A-A cross section of FIG. 2A.

A holder recess 26 concave from the upper end surface of the holder 23 is formed on the upper end surface of the holder 23, and the upper end of the bypass passage hole 25 is opened in the holder recess 26. Moreover, it is not limited to this, The structure which the upper end part of the bypass passage hole 25 opens in the upper end surface of the holder 23 may be sufficient, without forming the holder recessed part 26. FIG.

A head end surface 45 orthogonal to the central axis O is formed at the lower end of the cylinder head 40, and the upper end surface of the holder 23 is in contact with the head end surface 45.

On the head end surface 45, a bypass concave portion 46 which is concave in a disk shape centering on the central axis O is formed. The bypass concave portion 46 is formed to face the holder concave portion 26 of the holder 23 and the open end of the bypass passage hole 25, and the holder concave portion 26 and the bypass passage hole 25 are formed. The bypass passage 50 is partitioned between the open end of the () and the bypass recess 46.

When the piston rod 30 reaches near the stroke end during the extension operation of the hydraulic cylinder 1, the hydraulic fluid of the rod chamber 2 is moved to the bypass passage 50 and the supply / discharge passage 5 as indicated by the arrows in FIG. 2A. Pass through and outflow to hydraulic source.

A notch 29 is formed on the lower end surface of the holder 23. Accordingly, in the state where the hydraulic cylinder 1 is most extended, the upper end surface 22 of the piston 20 contacts the lower end surface of the holder 23. At this time, the cushion gap 4 and the bypass passage 50 communicate with the rod chamber 2 through the cutout 29.

The orifice 64 imparts resistance to the hydraulic oil flowing through the bypass passage 50. As a result, the cushion pressure of the rod chamber 2 increases, and the piston rod 30 is decelerated. The opening diameter and the passage length of the orifice 64 are set in accordance with the deceleration characteristics required for the cushion mechanism 6.

In the bypass passage 50, the hydraulic oil having passed through the orifice 64 flows out into the gap between the holder recess 26 of the holder 23 and the bypass recess 46 of the cylinder head 40, and It bends in the direction toward the central axis O about the inner wall surface of the path recess 46. As a result, noise is prevented from being generated by the flow of the hydraulic oil passing through the orifice 64.

An outer circumferential threaded portion (male screw) 66 is formed on the outer circumference of the cylindrical resistor 63. On the other hand, the inner circumferential threaded portion 27 is formed in the bypass passage hole 25 of the holder 23. The resistor 63 is provided by screwing the outer circumferential thread portion 66 to the inner circumferential thread portion 27 of the holder 23. Since the holder 23 is provided separately from the cylinder head 40, the machining of the bypass passage hole 25 can be easily performed, and the cost of the product can be reduced.

On the inner circumference of the resistor 63, an orifice 64 and a hexagonal hole 65 are formed together. The resistor 63 is fastened and fixed to the inner circumferential threaded portion 27 by a tool (not shown) engaged with the hexagonal hole 65.

In addition, it is not limited to this, The resistor 63 may be set as the structure which press-fits into the bypass passage hole 25 of the holder 23, and is provided. In addition, although the resistor 63 was interposed in the upper end part of the bypass passage hole 25 of the holder 23, it is not limited to this, You may mount in the lower end part of the bypass passage hole 25.

In addition, the through-hole which partitions the bypass passage 50 in the holder 23 is formed so that it may extend in the direction substantially orthogonal to the central axis O, and the resistor 63 is interposed in this through-hole. You may make it. In this case, the opening end of the passage hole is opposed to the cylinder inner circumferential surface 11, and the dropping of the resistor 63 by the cylinder inner circumferential surface 11 is supported.

The length (curvature radius) R1 from the central axis O to the outer circumferential wall portion defining the bypass concave portion 46 of the cylinder head 40 is the outer circumferential end portion of the resistor 63 from the central axis O. It is formed smaller than the length R2. As shown in FIG. 2B, a part of the head end face 45 of the cylinder head 40 replaces a part of the resistor 63.

As a result, even if the resistor 63 which is screwed to the inner circumferential threaded portion 27 of the holder 23 is released and protrudes upward from the bypass through-hole 25, a part of the resistor 63 is formed in the cylinder head 40. In contact with the head end surface 45, the resistor 63 is prevented from protruding further upwards. In this state, the bypass passage hole 25 communicates with the bypass recess 46. Accordingly, the resistor 63 is prevented from being dropped from the bypass through hole 25 of the holder 23, and the operation of the cushion mechanism 6 is maintained because the bypass passage 50 is not blocked.

The cushion bearing 60 is fitted with respect to the piston rod 30 so as to have a bearing inner circumferential gap 7 in the radial direction, and is floatably supported with respect to the piston rod 30. The bearing inner circumferential gap 7 is partitioned between the inner circumferential surface 67 of the cushion bearing 60 and the end outer circumferential surface 33 of the piston rod 30.

The cushion bearing 60 is interposed with the piston rod 30 so as to have a gap 8 in the central axis O direction. In the state where the lower end surface of the cushion bearing 60 is in contact with the upper end surface 22 of the piston 20, the gap 8 is a ring of the upper end surface 68 of the cushion bearing 60 and the piston rod 30. A partition is formed between the shape steps 32.

The notch 69 is formed in the lower end surface of the cushion bearing 60. In a state where the lower end surface of the cushion bearing 60 is in contact with the upper end surface 22 of the piston 20, the cutout 69 communicates with the bearing inner circumferential gap 7 and the rod chamber 2.

3 is a cross-sectional view showing a state when the piston rod 30 reaches the stroke end when the hydraulic cylinder 1 moves upward as shown by a white arrow. to be.

When the piston rod 30 reaches near the stroke end, the cushion bearing 60 enters the inside of the holder 23, so that the cushion gap 4 is formed therebetween.

The cushion gap 4 imparts resistance to the flow of hydraulic oil flowing out of the rod chamber 2 into the supply and discharge passage 5, and the cushion pressure of the rod chamber 2 rises. As a result, the cushion bearing 60 is pushed upward, the upper end surface of the cushion bearing 60 contacts the annular step portion 32 of the piston rod 30, and the gap 8 is closed to close the bearing inner peripheral gap 7. ) And the supply / discharge passage 5 are blocked.

As a result, the hydraulic oil of the rod chamber 2 passes through the cushion gap 4 and the bypass passage 50, respectively, as indicated by the arrow in FIG. 3, and flows out from the supply / discharge passage 5. The cushion gap 4 and the orifice 64 of the bypass passage 50 impart resistance to the flow of hydraulic oil flowing out of the rod chamber 2, and the cushion pressure of the rod chamber 2 rises, thereby increasing the piston rod 30. ) Is decelerated.

4 is a cross-sectional view showing the state when the piston rod 30 reaches the stroke end in the contracting operation of the hydraulic cylinder 1 moving downward as indicated by the white arrow. to be.

When pressurized hydraulic oil is supplied from the hydraulic source to the supply and discharge passage 5, the cushion bearing 60 is pressed downward, and the upper end surface of the cushion bearing 60 is spaced apart from the annular step portion 32 of the piston rod 30. The gap 8 is partitioned between the two, and the gap between the bearing inner peripheral gap 7 and the supply / discharge passage 5 is opened.

Accordingly, the pressurized hydraulic oil supplied to the supply / discharge passage 5 flows into the rod chamber 2 through the gap 8, the bearing inner circumferential gap 7, and the cutout 69, as indicated by arrows in FIG. 4. Together, they flow through the cushion gap 4 and the bypass passage 50, respectively. Since the hydraulic fluid flows into the rod chamber 2 through the three flow paths as described above, the piston rod 30 moves in the contracting direction quickly.

Thus, the cushion bearing 60 functions as a check valve which closes the bearing inner circumferential gap 7 during the stretching operation near the stroke end, and opens the bearing inner circumferential gap 7 during the contracting operation.

The gist, action, and effect of the present embodiment will be described below.

The hydraulic cylinder 1 of this embodiment is provided with the cushion mechanism 6 which slows down the piston rod 30 in the vicinity of the stroke end of the piston rod 30 with respect to the cylinder tube 10. The cushion mechanism 6 includes a cushion bearing 60 provided on the piston rod 30, a cushion cylindrical surface 24 into which the cushion bearing 60 enters near the stroke end, the cushion cylindrical surface 24, and a cushion. A cushion gap 4 formed between the bearings 60 to narrow the flow of the working fluid, a bypass passage 50 for guiding the working fluid bypassing the cushion gap 4, and the bypass passage 50. ) Is provided with a resistor (63) interposed. In the resistor 63, an orifice 64 is formed that narrows the flow of the working fluid through the bypass passage 50.

Accordingly, by changing the shape or size of the orifice 64 formed in the resistor 63, the resistance given to the flow of the hydraulic oil passing through the bypass passage 50 can be adjusted, and a predetermined cushion pressure can be obtained. have.

Since the orifice 64 is formed in the resistor 63 interposed in the bypass passage 50, the holder 23 which partitions the bypass passage 50 can be common among products of different specifications, It is possible to cope with different specifications simply by changing the resistor 63 without increasing the product number of the holder 23. Moreover, compared with the case where an orifice is formed in the holder 23 which partitions the bypass passage 50, the processing precision of the orifice 64 can be improved, and the dispersion | variation in cushion performance can be suppressed.

Since it is not necessary to mount the cushion seal inside the cushion bearing 60 like the conventional apparatus, it is possible to reduce the cost of the product and to eliminate the variation in the cushion performance related to the cushion seal.

Since it is not necessary to form the cushion seal groove | channel in which the cushion seal is interposed in the outer periphery of the piston rod 30 like a conventional apparatus, the intensity | strength of the piston rod 30 can be improved.

In the present embodiment, the cushion mechanism 6 includes a cylinder head 40 for slidingly supporting the piston rod 30 and an annular shape interposed with the cylinder head 40 inside the cylinder tube 10. Holder 23 is provided. The holder 23 has a cushion cylindrical surface 24 and a bypass passage hole 25 in which a part of the bypass passage 50 is formed so that the resistor 63 is interposed. The cylinder head 40 is recessed in the head end surface 45 opposed to the opening end of the bypass passage hole 25 and the head end surface 45 to form a part of the bypass passage 50. The length R1 from the central axis O to the outer circumferential wall portion that defines the bypass recess 46 is defined by a resistor from the central axis O of the piston rod 30. Since it is set smaller than the length R2 to the outer circumferential end of the 63, it is supported that the resistor 63 is pulled out of the bypass passage hole 25.

Thereby, while the resistor 63 is prevented from falling out of the bypass passage hole 25 of the holder 23 and the bypass passage 50 is not blocked, the operation of the cushion mechanism 6 can be maintained. .

In addition, since the holder 23 to which the resistor 63 is interposed is formed separately from the cylinder head 40, cushion performance is facilitated by replacing the holder 23 and the resistor 63 according to the required deceleration characteristics. I can adjust it.

In this embodiment, the head end surface 45 which opposes the bypass passage hole 25 is formed in the cylinder head 40.

Thereby, the cushion mechanism 6 can be comprised by adding the holder 23, without changing the basic shape of the cylinder head 40, and can suppress the cost increase of a product.

In this embodiment, the cushioning mechanism 6 is partitioned between the cylinder head 40 which supports the piston rod 30 so that sliding is possible, and the piston rod 30 and the cylinder head 40, and rapidly delivers a working fluid. The supply-discharge passage 5 is provided. The cushion bearing 60 is floated and supported so that the piston rod 30 may have a bearing inner peripheral gap 7. When the cushion bearing 60 enters the cushion cylindrical surface 24, the gap between the bearing inner circumferential gap 7 and the supply / discharge passage 5 is blocked, while the cushion bearing 60 is removed from the cushion cylindrical surface 24. In the outgoing operation, the gap between the bearing inner circumferential gap 7 and the supply and discharge passage 5 is opened.

Accordingly, since the cushion bearing 60 functions as a check valve for opening and closing between the bearing inner circumferential gap 7 and the supply / discharge passage 5, the piston rod 30 can be moved quickly when the fluid pressure cylinder 1 is driven. Can be.

As mentioned above, although embodiment of this invention was described, the said embodiment is only a part of application example of this invention, and is not the meaning which limits the technical scope of this invention to the specific structure of the said embodiment.

For example, a plurality of annular grooves (labyrinth grooves) are formed in the inner circumferential surface 67 of the cushion bearing 60 defining the bearing inner circumferential gap 7 and the end outer circumferential surface 33 of the piston rod 30. Also good. Thereby, resistance to the working fluid flowing through the bearing inner circumferential gap 7 can be maintained to coaxially hold the cushion bearing 60 with respect to the piston rod 30.

In addition, in the said embodiment, although the cushion mechanism decelerated the piston rod at the time of the extending operation of the hydraulic cylinder 1, the piston rod was near the stroke end of the piston rod at the time of the contraction operation of the hydraulic cylinder 1 May be configured to reduce the speed.

This application claims priority based on Japanese Patent Application No. 2011-193792 for which it applied to Japan Patent Office on September 6, 2011, and all the content of this application is integrated in this specification by reference.

Claims (3)

A fluid pressure cylinder having a cushioning mechanism for decelerating the piston rod near the stroke end of the piston rod relative to the cylinder tube,
The cushion mechanism,
A cushion bearing installed on the piston rod,
A cushion cylindrical surface into which the cushion bearing enters near the stroke end,
A cushion gap formed between the cushion cylindrical surface and the cushion bearing to narrow the flow of the working fluid;
A bypass passage for inducing a working fluid bypassing the cushion gap;
Resistors interposed in the bypass passage
And,
And a orifice formed in the resistor to narrow the flow of working fluid through the bypass passage. The method of claim 1,
The cushion mechanism,
A cylinder head for slidingly supporting the piston rod;
An annular holder interposed with the cylinder head inside the cylinder tube
And,
The holder has a cushion cylindrical surface and a bypass passage hole through which the resistor is interposed to define a part of the bypass passage,
The cylinder head has a head end face opposed to the open end of the bypass passage hole, and a bypass recess formed in the head end face to partition a part of the bypass passage,
And a length from the central axis of the piston rod to the outer circumferential wall portion that defines the bypass recess is smaller than the length from the central axis of the piston rod to the outer circumferential end of the resistor. The method of claim 1,
The cushion mechanism,
A cylinder head for slidingly supporting the piston rod;
A distribution passage formed between the piston rod and the cylinder head to supply and supply a working fluid
And,
The cushion bearing is floating supported to have a bearing inner circumferential gap with respect to the piston rod,
Between the bearing inner circumferential gap and the supply / discharge passage is closed when the cushion bearing enters the cushion cylindrical surface, and between the bearing inner circumferential gap and the supply / discharge passage when the cushion bearing exits the cushion cylindrical surface The hydraulic pressure cylinder is opened.

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